Semiconductor packages and methods of forming the same

ABSTRACT

A method includes forming a first redistribution structure by depositing a first dielectric layer and forming first and second conductive features on the first dielectric layer, the second conductive feature being provided with a gap exposing the first dielectric layer. The method further includes depositing a second dielectric layer on the first and second conductive features; forming first and second openings in the second dielectric layer, the first opening exposing the first conductive feature and the second opening exposing the second conductive feature and the gap; forming a first via on the first conductive feature and partially in the first opening; forming a second via on the second conductive feature and partially in the second opening and the gap; attaching a die to the first redistribution structure adjacent the first via and the second via; and encapsulating the die, the first via, and the second via with an encapsulant.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.16/390,275, filed Apr. 22, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/782,993, filed Oct. 13, 2017, now issued U.S.Pat. No. 10,269,773, which claims the benefit of U.S. ProvisionalApplication No. 62/565,321, filed Sep. 29, 2017, which applications areincorporated herein by reference.

BACKGROUND

The semiconductor industry has experienced rapid growth due to ongoingimprovements in the integration density of a variety of electroniccomponents (e.g., transistors, diodes, resistors, capacitors, etc.). Forthe most part, improvement in integration density has resulted fromiterative reduction of minimum feature size, which allows morecomponents to be integrated into a given area. As the demand forshrinking electronic devices has grown, a need for smaller and morecreative packaging techniques of semiconductor dies has emerged. Anexample of such packaging systems is Package-on-Package (PoP)technology. In a PoP device, a top semiconductor package is stacked ontop of a bottom semiconductor package to provide a high level ofintegration and component density. PoP technology generally enablesproduction of semiconductor devices with enhanced functionalities andsmall footprints on a printed circuit board (PCB).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 14 are various views of intermediate steps during aprocess for forming a device package, in accordance with someembodiments.

FIGS. 15 through 18 are various views of intermediate steps during aprocess for forming a package structure, in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Semiconductor packages and methods of forming the same are disclosed,according to some embodiments. In particular, a first redistributionstructure is formed having redistribution lines. A first via is formedextending from a surface of a first conductive feature. A second via isformed extending from a gap between a second and third conductivefeature. The second via is longer than the first via. Conductiveconnectors, such as solder, are attached to the back side of the firstredistribution structure. A first conductive connector is coupled to thefirst conductive feature, and is offset from the first via. As a result,an intermetallic compound (IMC) formed during reflow does not extendlaterally to the first via. A second conductive connector is coupled tothe second and third conductive features, and is aligned with the secondvia. As a result, when an IMC formed during reflow, copper is diffusedfrom the second via, and not from the second and third conductivefeatures. Avoiding diffusion of copper from the second and thirdconductive features may avoid delamination of seed layers used duringformation of the vias.

FIGS. 1 through 14 are various views of intermediate steps during aprocess for forming a device package 200, in accordance with someembodiments. FIGS. 1 through 14 are cross-sectional views. The devicepackage 200 may be referred to as an integrated fan-out (InFO) package.

In FIG. 1 , the device package 200 is shown at an intermediate stage ofprocessing including a release layer 102 formed on a carrier substrate100. A package region 600 for the formation of the device package 200 isillustrated. Although only one package region is shown, there may bemany package regions formed.

The carrier substrate 100 may be a glass carrier substrate, a ceramiccarrier substrate, or the like. The carrier substrate 100 may be awafer, such that multiple packages can be formed on the carriersubstrate 100 simultaneously. The release layer 102 may be formed of apolymer-based material, which may be removed along with the carriersubstrate 100 from the overlying structures that will be formed insubsequent steps. In some embodiments, the release layer 102 is anepoxy-based thermal-release material, which loses its adhesive propertywhen heated, such as a light-to-heat-conversion (LTHC) release coating.In other embodiments, the release layer 102 may be an ultra-violet (UV)glue, which loses its adhesive property when exposed to UV lights. Therelease layer 102 may be dispensed as a liquid and cured, may be alaminate film laminated onto the carrier substrate 100, or may be thelike. The top surface of the release layer 102 may be leveled and mayhave a high degree of coplanarity.

In FIG. 2 , a dielectric layer 104 is formed on the release layer 102.The bottom surface of the dielectric layer 104 may be in contact withthe top surface of the release layer 102. In some embodiments, thedielectric layer 104 is formed of a polymer, such as polybenzoxazole(PBO), polyimide, benzocyclobutene (BCB), or the like. In otherembodiments, the dielectric layer 104 is formed of a nitride such assilicon nitride; an oxide such as silicon oxide, phosphosilicate glass(PSG), borosilicate glass (BSG), boron-doped phosphosilicate glass(BPSG), or the like; or the like. The dielectric layer 104 may be formedby any acceptable deposition process, such as spin coating, chemicalvapor deposition (CVD), laminating, the like, or a combination thereof.

In FIG. 3 , a seed layer 106 is formed over the dielectric layer 104. Insome embodiments, the seed layer 106 is a metal layer, which may be asingle layer or a composite layer comprising a plurality of sub-layersformed of different materials. In some embodiments, the seed layer 106includes a titanium layer and a copper layer over the titanium layer.The seed layer 106 may be formed using, for example, PVD or the like.

In FIG. 4 , a metallization pattern 108 is formed over the dielectriclayer 104. A photo resist (not shown) is formed and patterned on theseed layer 106. The photo resist may be formed by spin coating or thelike and may be exposed to light for patterning. The pattern of thephoto resist corresponds to the metallization pattern 108. Thepatterning forms openings through the photo resist to expose the seedlayer 106. A conductive material is formed in the openings of the photoresist and on the exposed portions of the seed layer 106. The conductivematerial may be formed by plating, such as electroplating or electrolessplating, or the like. The conductive material may be a metal or a metalalloy, such as copper, titanium, tungsten, aluminum, the like, orcombinations thereof. Then, the photo resist and portions of the seedlayer 106 on which the conductive material is not formed are removed.The photo resist may be removed by an acceptable ashing or strippingprocess, such as using an oxygen plasma or the like. Once the photoresist is removed, exposed portions of the seed layer 106 are removed,such as by using an acceptable etching process, such as by wet or dryetching. The remaining portions of the seed layer 106 and conductivematerial form the metallization pattern 108.

The conductive features of the metallization pattern 108 may be referredto as redistribution layers or redistribution lines. The redistributionlines may not be formed to have a uniform width, and some of theredistribution lines may include multiple conductive features. Firstredistribution lines 108A may each include a single conductive featurethat will be electrically connected to devices of the device package200. Second redistribution lines 108B may each include a plurality ofconductive features that are separated by a gap 110, and areelectrically connected together and to devices of the device package200. The combined width W_(B) of the second redistribution lines 108Bmay be substantially equal to the width W_(A) of the firstredistribution lines 108A, or may be different.

In some embodiments, the conductive features of the secondredistribution lines 108B are formed separately during formation of themetallization pattern 108, e.g., each conductive feature may correspondto an opening in the photo resist exposing the seed layer 106. In someembodiments, a single conductive feature is formed during formation ofthe metallization pattern 108, and the gaps 110 are formed afterwardsusing acceptable etching techniques to divide the single conductivefeature into a plurality of conductive features. The gaps 110 are formedto have a width W_(G). The gaps 110 may extend from top surfaces of thesecond redistribution lines 108B to bottom surfaces of the secondredistribution lines 108B such that the dielectric layer 104 is exposed.The gaps 110 may be formed in a center of the second redistributionlines 108B such that the conductive features of the secondredistribution lines 108B are a same length, or may be formed offsetfrom the center of the second redistribution lines 108B such that theconductive features of the second redistribution lines 108B are adifferent length.

In FIG. 5 , a dielectric layer 112 is formed on the metallizationpattern 108 and the dielectric layer 104. In some embodiments, thedielectric layer 112 is formed of a polymer, which may be aphoto-sensitive material such as PBO, polyimide, BCB, or the like, thatmay be patterned using a lithography mask. In other embodiments, thedielectric layer 112 is formed of a nitride such as silicon nitride; anoxide such as silicon oxide, PSG, BSG, BPSG; or the like. The dielectriclayer 112 may be formed by spin coating, lamination, CVD, the like, or acombination thereof.

The dielectric layer 112 is then patterned to form openings 114 toexpose portions of the metallization pattern 108. The patterning may beby an acceptable process, such as by exposing the dielectric layer 112to light when the dielectric layer is a photo-sensitive material or byetching using, for example, an anisotropic etch. First openings 114A areformed exposing the first redistribution lines 108A, and second openings114B are formed exposing the second redistribution lines 108B. Thesecond openings 114B are formed over the gaps 110 of the secondredistribution lines 108B; as such, sides of the conductive features areexposed, portions of the top surfaces of the conductive features areexposed, and portions of the dielectric layer 104 are exposed. In theillustrated embodiment, the first openings 114A and second openings 114Beach have a same width Wo. In other embodiments, the first openings 114Aand second openings 114B have different widths. The width Wo of theopenings 114 is greater than the width W_(G) of the gaps 110.

The openings 114 may be formed over a center of each of themetallization patterns 108, or may be formed offset from the center. Inthe embodiment shown, the first openings 114A are formed offset from thecenters of the metallization patterns 108, and the second openings 114Bare formed over centers of the metallization patterns 108.

The dielectric layers 104 and 112 and the metallization patterns 108 maybe referred to as a back-side redistribution structure 116. Asillustrated, the back-side redistribution structure 116 includes the twodielectric layers 104 and 112 and one metallization pattern 108. Inother embodiments, the back-side redistribution structure 116 caninclude any number of dielectric layers, metallization patterns, andvias. One or more additional metallization patterns and dielectriclayers may be formed in the back-side redistribution structure 116 byrepeating the processes for forming the metallization patterns 108 anddielectric layer 112. Vias may be formed during the formation of ametallization pattern by forming the seed layer and conductive materialof the metallization pattern in the opening of the underlying dielectriclayer. The vias may therefore interconnect and electrically couple thevarious metallization patterns.

In FIG. 6 , a seed layer 118 is formed over the back-side redistributionstructure 116 and in the openings 114. The seed layer 118 is over thedielectric layer 112, exposed portions of the metallization pattern 108,and exposed portions of the dielectric layer 104. In some embodiments,the seed layer 118 is a metal layer, which may be a single layer or acomposite layer comprising a plurality of sub-layers formed of differentmaterials. In some embodiments, the seed layer 118 comprises a titaniumlayer and a copper layer over the titanium layer. The seed layer 118 maybe formed using, for example, PVD or the like.

In FIG. 7 , a photo resist 120 is formed and patterned on the seed layer118. The photo resist 120 may be formed by spin coating or the like andmay be exposed to light for patterning. The pattern of the photo resist120 corresponds to through vias that will be subsequently formed. Thepatterning forms openings through the photo resist 120 to expose theseed layer 118. The openings through the photo resist 120 are disposedover the openings 114 in the dielectric layer 112, and may have a samewidth W_(P) over both the first openings 114A and second openings 114B.The width W_(P) of the openings is greater than the width Wo of theopenings 114.

In FIG. 8 , a conductive material is formed in the openings of the photoresist 120 and on the exposed portions of the seed layer 118. Theconductive material may be formed by plating, such as electroplating orelectroless plating, or the like. The conductive material may be a metalor a metal alloy, such as copper, titanium, tungsten, aluminum, thelike, or combinations thereof. The photo resist 120 and portions of theseed layer 118 on which the conductive material is not formed areremoved. The photo resist may be removed by an acceptable ashing orstripping process, such as using an oxygen plasma or the like. Once thephoto resist is removed, exposed portions of the seed layer 118 areremoved, such as by using an acceptable etching process, such as by wetor dry etching. The remaining portions of the seed layer and conductivematerial form through vias 122 electrically connected to theredistribution lines.

Because the seed layer 118 is formed in the gaps 110 of the secondredistribution lines 108B, second vias 122B are formed extending throughthe second redistribution lines 108B. Conversely, first vias 122A areformed on the first redistribution lines 108A, and do not extend throughthe first redistribution lines 108A. The first vias 122A and second vias122B may both have the same width W_(P) over the dielectric layer 112,and the same width Wo in the openings 114. The second vias 122B havealso the width W_(G) in the gaps 110. Because the second vias 122B havethree different widths, each of a descending width, the second vias 122Bmay be referred to as having a ladder structure. Because the firstopenings 114A were formed offset from the centers of the metallizationpatterns 108, the first vias 122A are formed offset from the centers ofthe first redistribution lines 108A.

Although the first vias 122A are illustrated as having one change inwidths, and the second vias 122B are illustrated as having two changesin widths, it should be appreciated that the first vias 122A and secondvias 122B may have any quantity of changes in widths in otherembodiments. According to embodiments, the second vias 122B have morechanges in widths than the first vias 122A.

In FIG. 9 , integrated circuit dies 124 are adhered to the dielectriclayer 112 by an adhesive 126. As illustrated in FIG. 4 , one integratedcircuit die 124 is adhered in the package region 600. In otherembodiments, multiple integrated circuit dies 124 may be adhered in eachregion. The integrated circuit dies 124 may be bare dies, such as, logicdies (e.g., central processing unit, microcontroller, etc.), memory dies(e.g., dynamic random access memory (DRAM) die, static random accessmemory (SRAM) die, etc.), power management dies (e.g., power managementintegrated circuit (PMIC) die), radio frequency (RF) dies, sensor dies,micro-electro-mechanical-system (MEMS) dies, signal processing dies(e.g., digital signal processing (DSP) die), front-end dies (e.g.,analog front-end (AFE) dies), the like, or a combination thereof. Also,in some embodiments, the integrated circuit dies 124 in the differentpackage regions (now shown) may be different sizes (e.g., differentheights and/or surface areas), and in other embodiments, the integratedcircuit dies 124 may be the same size (e.g., same heights and/or surfaceareas).

Before being adhered to the dielectric layer 112, the integrated circuitdies 124 may be processed according to applicable manufacturingprocesses to form integrated circuits in the integrated circuit dies124. For example, the integrated circuit dies 124 each include asemiconductor substrate 128, such as silicon, doped or undoped, or anactive layer of a semiconductor-on-insulator (SOI) substrate. Thesemiconductor substrate may include other semiconductor materials, suchas germanium; a compound semiconductor including silicon carbide,gallium arsenic, gallium phosphide, indium phosphide, indium arsenide,and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP,AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof.Other substrates, such as multi-layered or gradient substrates, may alsobe used. Devices, such as transistors, diodes, capacitors, resistors,etc., may be formed in and/or on the semiconductor substrate 128 and maybe interconnected by interconnect structures 130 formed by, for example,metallization patterns in one or more dielectric layers on thesemiconductor substrate 128 to form an integrated circuit.

The integrated circuit dies 124 further comprise pads 132, such asaluminum pads, to which external connections are made. The pads 132 areon what may be referred to as respective active sides of the integratedcircuit dies 124. Passivation films 134 are on the integrated circuitdies 124 and on portions of the pads 132. Openings are through thepassivation films 134 to the pads 132. Die connectors 136, such asconductive pillars (for example, comprising a metal such as copper), arein the openings through the passivation films 134 and are mechanicallyand electrically coupled to the respective pads 132. The die connectors136 may be formed by, for example, plating, or the like. The dieconnectors 136 electrically couple the respective integrated circuits ofthe integrated circuit dies 124.

A dielectric material 138 is on the active sides of the integratedcircuit dies 124, such as on the passivation films 134 and the dieconnectors 136. The dielectric material 138 laterally encapsulates thedie connectors 136, and the dielectric material 138 is laterallycoterminous with the respective integrated circuit dies 124. Thedielectric material 138 may be initially formed to bury or cover the dieconnectors 136; when the die connectors 136 are buried, the top surfaceof the dielectric material 138 may have an uneven topology. Thedielectric material 138 may be a polymer such as PBO, polyimide, BCB, orthe like; a nitride such as silicon nitride or the like; an oxide suchas silicon oxide, PSG, BSG, BPSG, or the like; the like, or acombination thereof, and may be formed, for example, by spin coating,lamination, CVD, or the like.

The adhesive 126 is on back-sides of the integrated circuit dies 124 andadheres the integrated circuit dies 124 to the back-side redistributionstructure 116, such as the dielectric layer 112 in the illustration. Theadhesive 126 may be any suitable adhesive, epoxy, die attach film (DAF),or the like. The adhesive 126 may be applied to a back-side of theintegrated circuit dies 124, such as to a back-side of the respectivesemiconductor wafer or may be applied over the surface of the carriersubstrate 100. The integrated circuit dies 124 may be singulated, suchas by sawing or dicing, and adhered to the dielectric layer 112 by theadhesive 126 using, for example, a pick-and-place tool.

Although the integrated circuit dies 124 are illustrated and describedabove as being bare dies (e.g., unpackaged dies), in other embodiments,the integrated circuit dies 124 may be packaged chips (e.g., one or morebare dies integrated with other package features, such as,redistribution structures, passive devices, etc.). For example, theintegrated circuit dies 124 may be a memory package (e.g., a hybridmemory cube) comprising a plurality of stacked and interconnected memorydies.

In FIG. 10 , an encapsulant 140 is formed on the various components. Theencapsulant 140 may be a molding compound, epoxy, or the like, and maybe applied by compression molding, transfer molding, or the like. Theencapsulant 140 may be formed over the carrier substrate 100 such thatthe die connectors 136 of the integrated circuit dies 124 and/or thethrough vias 122 are buried or covered. The encapsulant 140 is thencured.

In FIG. 11 , a planarization process is performed on the encapsulant 140to expose the through vias 122 and the die connectors 136. Theplanarization process may also grind the dielectric material 138. Topsurfaces of the through vias 122, die connectors 136, dielectricmaterial 138, and encapsulant 140 are coplanar after the planarizationprocess. The planarization process may be, for example, achemical-mechanical polish (CMP), a grinding process, or the like. Insome embodiments, the planarization may be omitted, for example, if thethrough vias 122 and die connectors 136 are already exposed. As notedabove, the second vias 122B extend through the metallization pattern108. As such, after the planarization process, the second vias 122B arelonger than the first vias 122A when the first vias 122A and the secondvias 122B are connected to a same metallization layer of the back-sideredistribution structure 116.

In FIG. 12 , a front-side redistribution structure 142 is formed on theencapsulant 140, the through vias 122, and the die connectors 136. Thefront-side redistribution structure 142 includes multiple dielectriclayers and metallization patterns. For example, the front-sideredistribution structure 142 may be patterned as a plurality of discretemetallization patterns separated from each other by respectivedielectric layer(s).

In some embodiments, the dielectric layers are formed of a polymer,which may be a photo-sensitive material such as PBO, polyimide, BCB, orthe like, may be patterned using a lithography mask. In otherembodiments, the dielectric layers are formed of a nitride such assilicon nitride; an oxide such as silicon oxide, PSG, BSG, BPSG; or thelike. The dielectric layers may be formed by spin coating, lamination,CVD, the like, or a combination thereof.

After formation, the dielectric layers are patterned to exposeunderlying conductive features. The bottom dielectric layer is patternedto expose portions of the through vias 122 and the die connectors 136,and intermediate dielectric layer(s) are patterned to expose portions ofunderlying metallization patterns. The patterning may be by anacceptable process, such as by exposing the dielectrics layer to lightwhen the dielectric layers are a photo-sensitive material, or by etchingusing, for example, an anisotropic etch. If the dielectric layers arephoto-sensitive materials, the dielectric layers can be developed afterthe exposure.

Metallization patterns with vias are formed on each dielectric layer. Aseed layer (not shown) is formed over the dielectric layer and inopenings through the dielectric layer. In some embodiments, the seedlayer is a metal layer, which may be a single layer or a composite layercomprising a plurality of sub-layers formed of different materials. Insome embodiments, the seed layer comprises a titanium layer and a copperlayer over the titanium layer. The seed layer may be formed using adeposition process, such as PVD or the like. A photo resist is thenformed and patterned on the seed layer. The photo resist may be formedby spin coating or the like and may be exposed to light for patterning.The pattern of the photo resist corresponds to the metallizationpattern. The patterning forms openings through the photo resist toexpose the seed layer. A conductive material is formed in the openingsof the photo resist and on the exposed portions of the seed layer. Theconductive material may be formed by plating, such as electroplating orelectroless plating, or the like. The conductive material may comprise ametal or a metal alloy, such as copper, titanium, tungsten, aluminum,the like, or combinations thereof. Then, the photo resist and portionsof the seed layer on which the conductive material is not formed areremoved. The photo resist may be removed by an acceptable ashing orstripping process, such as using an oxygen plasma or the like. Once thephoto resist is removed, exposed portions of the seed layer are removed,such as by using an acceptable etching process, such as by wet or dryetching. The remaining portions of the seed layer and conductivematerial form the metallization pattern and vias for one metallizationlevel of the front-side redistribution structure 142.

The front-side redistribution structure 142 is shown as an example. Moreor fewer dielectric layers and metallization patterns than shown may beformed in the front-side redistribution structure 142. One havingordinary skill in the art will readily understand which steps andprocesses would be omitted or repeated to form more or fewer dielectriclayers and metallization patterns.

The top dielectric layer of the front-side redistribution structure 142is patterned to expose portions of the metallization patterns for theformation of conductive pads. The conductive pads are used to couple toconductive connectors, and may be referred to as under bump metallurgies(UBMs) 144. The patterning may be by an acceptable process, such as byexposing the top dielectric layer to light when the top dielectric layeris a photo-sensitive material or by etching using, for example, ananisotropic etch. If the top dielectric layer is a photo-sensitivematerial, the top dielectric layer can be developed after the exposure.The UBMs 144 are then formed on the exterior side of the front-sideredistribution structure 142. The UBMs 144 are formed extending throughopenings in the top dielectric layer to contact the metallization layersof the front-side redistribution structure 142.

As an example to form the UBMs 144, a seed layer (not shown) is formedover the top dielectric layer and in openings through the top dielectriclayer. In some embodiments, the seed layer is a metal layer, which maybe a single layer or a composite layer comprising a plurality ofsub-layers formed of different materials. In some embodiments, the seedlayer comprises a titanium layer and a copper layer over the titaniumlayer. The seed layer may be formed using a deposition process, such asPVD or the like. A photo resist is then formed and patterned on the seedlayer. The photo resist may be formed by spin coating or the like andmay be exposed to light for patterning. The pattern of the photo resistcorresponds to the pattern of the conductive pads in the front-sideredistribution structure 142. The patterning forms openings through thephoto resist to expose the seed layer. A conductive material is formedin the openings of the photo resist and on the exposed portions of theseed layer. The conductive material may be formed by plating, such aselectroplating or electroless plating, or the like. The conductivematerial may comprise a metal or a metal alloy, such as copper,titanium, tungsten, aluminum, the like, or combinations thereof. Then,the photo resist and portions of the seed layer on which the conductivematerial is not formed are removed. The photo resist may be removed byan acceptable ashing or stripping process, such as using an oxygenplasma or the like. Once the photo resist is removed, exposed portionsof the seed layer are removed, such as by using an acceptable etchingprocess, such as by wet or dry etching. The remaining portions of theseed layer and conductive material form the UBMs 144.

Conductive connectors 146 are formed on the UBMs 144. The conductiveconnectors 146 may be BGA connectors, solder balls, metal pillars,controlled collapse chip connection (C4) bumps, micro bumps, electrolessnickel-electroless palladium-immersion gold technique (ENEPIG) formedbumps, or the like. The conductive connectors 146 may be formed of ametal or metal alloy, such as solder, copper, aluminum, gold, nickel,silver, palladium, tin, the like, or a combination thereof. In someembodiments, the conductive connectors 146 are formed by initiallyforming a layer of solder through such commonly used methods such asevaporation, electroplating, printing, solder transfer, ball placement,or the like. Once a layer of solder has been formed on the structure, areflow may be performed in order to shape the material into the desiredbump shapes. In another embodiment, the conductive connectors 146 aremetal pillars (such as a copper pillar) formed by a sputtering,printing, electro plating, electroless plating, CVD, or the like. Themetal pillars may be solder free and have substantially verticalsidewalls. In some embodiments, a metal cap layer (not shown) is formedon the top of the UBMs 144. The metal cap layer may include nickel, tin,tin-lead, gold, silver, palladium, indium, nickel-palladium-gold,nickel-gold, the like, or a combination thereof and may be formed by aplating process.

In FIG. 13 , a carrier substrate de-bonding is performed to detach(de-bond) the carrier substrate 100 from the back-side redistributionstructure 116, e.g., the dielectric layer 104. In accordance with someembodiments, the de-bonding includes projecting a light such as a laserlight or an UV light on the release layer 102 so that the release layer102 decomposes under the heat of the light and the carrier substrate 100can be removed. The structure is then flipped over and placed on tape148.

Further in FIG. 13 , openings 150 are formed through the dielectriclayer 104 to expose portions of the metallization pattern 108. Theopenings may be formed, for example, using laser drilling, acceptableetching techniques, or the like. First openings 150A are formed exposingthe first redistribution lines 108A, and second openings 150B are formedexposing the second redistribution lines 108B. The first openings 150Aare formed offset from centers of the first vias 122A, such that thefirst openings 150A are disposed a distance D_(O) from portions of thefirst vias 122A in the dielectric layer 112. The second openings 150Bare formed centered under the second vias 122B such that the seed layer118 and portions of the seed layer 106 extending through the secondredistribution lines 108B are exposed.

In FIG. 14 , portions of the seed layers 106 and 118 exposed by theopenings 150 are thinned or completely removed. The exposed portions ofthe seed layers 106 and 118 may be thinned or removed by an acceptableetching process, such as by wet or dry etching. In embodiments where theseed layers 106 and 118 include multiple layers, the etching process mayremove some or all of the exposed multiple layers. In embodiments wherethe seed layers 106 and 118 include a titanium layer over the dielectriclayer 104 and a copper layer over the titanium layer, the etchingprocess may remove the titanium layer and leave the copper layer intact,thereby thinning the layer. In such embodiments, the etching process isperformed with one or more etchants that are selective to the titaniumlayer (e.g., that etch the titanium layer at a substantially higher ratethan the copper layer). In other embodiments, the exposed portions ofthe seed layers 106 and 118 are completely removed (e.g., all layers areremoved).

FIGS. 15 through 18 are various views of intermediate steps during aprocess for forming a package structure 400, in accordance with someembodiments. FIGS. 15 through 18 are cross-sectional views. The packagestructure 400 may be referred to a package-on-package (PoP) structure.

In FIG. 15 , a device package 300 is bonded to the device package 200.The device package 300 may be bonded to the device package 200 in eachpackage region 600. The device package 300 includes a substrate 302 andone or more stacked dies 308 (308A and 308B) coupled to the substrate302. Although a singular stack of dies 308 (308A and 308B) isillustrated, in other embodiments, a plurality of stacked dies 308 (eachhaving one or more stacked dies) may be disposed side by side coupled toa same surface of the substrate 302.

The substrate 302 may be made of a semiconductor material such assilicon, germanium, diamond, or the like. In some embodiments, compoundmaterials such as silicon germanium, silicon carbide, gallium arsenic,indium arsenide, indium phosphide, silicon germanium carbide, galliumarsenic phosphide, gallium indium phosphide, combinations of these, andthe like, may also be used. Additionally, the substrate 302 may be asilicon-on-insulator (SOI) substrate. Generally, an SOI substrateincludes a layer of a semiconductor material such as epitaxial silicon,germanium, silicon germanium, SOI, silicon germanium on insulator(SGOI), or combinations thereof. The substrate 302 is, in onealternative embodiment, based on an insulating core such as a fiberglassreinforced resin core. One example core material is fiberglass resinsuch as FR4. Alternatives for the core material includebismaleimide-triazine (BT) resin, or alternatively, other printedcircuit board (PCB) materials or films. Build up films such as Ajinomotobuild-up film (ABF) or other laminates may be used for substrate 302.

The substrate 302 may include active and/or passive devices (not shown).As one of ordinary skill in the art will recognize, a wide variety ofdevices such as transistors, capacitors, resistors, combinations ofthese, and the like may be used to generate the structural andfunctional requirements of the design for the device package 300. Thedevices may be formed using any suitable methods.

The substrate 302 may also include metallization layers (not shown) andthrough vias 306. The metallization layers may be formed over the activeand passive devices and are designed to connect the various devices toform functional circuitry. The metallization layers may be formed ofalternating layers of dielectric (e.g., low-k dielectric material) andconductive material (e.g., copper) with vias interconnecting the layersof conductive material and may be formed through any suitable process(such as deposition, damascene, dual damascene, or the like). In someembodiments, the substrate 302 is substantially free of active andpassive devices.

The substrate 302 may have bond pads 303 on a first side the substrate202 to couple to the stacked dies 308, and bond pads 304 on a secondside of the substrate 302, the second side being opposite the first sideof the substrate 302, to couple to the conductive connectors 314. Insome embodiments, the bond pads 303 and 304 are formed by formingrecesses (not shown) into dielectric layers (not shown) on the first andsecond sides of the substrate 302. The recesses may be formed to allowthe bond pads 303 and 304 to be embedded into the dielectric layers. Inother embodiments, the recesses are omitted as the bond pads 303 and 304may be formed on the dielectric layer. In some embodiments, the bondpads 303 and 304 include a thin seed layer (not shown) made of copper,titanium, nickel, gold, palladium, the like, or a combination thereof.The conductive material of the bond pads 303 and 304 may be depositedover the thin seed layer. The conductive material may be formed by anelectro-chemical plating process, an electroless plating process, CVD,ALD, PVD, the like, or a combination thereof. The conductive material ofthe bond pads 303 and 304 may be copper, tungsten, aluminum, silver,gold, nickel, the like, or a combination thereof.

In an embodiment, the bond pads 303 and 304 are UBMs that include threelayers of conductive materials, such as a layer of titanium, a layer ofcopper, and a layer of nickel. For example, the bond pads 304 mayinclude a layer of titanium (not shown), a main copper portion 304A, anda nickel finish 304B. The nickel finish 304B may improve the shelf lifeof the device package 300, which may be particularly advantageous whenthe device package 300 is a memory device such as a DRAM module.However, one of ordinary skill in the art will recognize that there aremany suitable arrangements of materials and layers, such as anarrangement of chrome/chrome-copper alloy/copper/gold, an arrangement oftitanium/titanium tungsten/copper, or an arrangement ofcopper/nickel/gold, that are suitable for the formation of the UBMs 303and 304. Any suitable materials or layers of material that may be usedfor the UBMs 303 and 304 are fully intended to be included within thescope of the current application. In some embodiments, the through vias306 extend through the substrate 302 and couple at least one bond pad303 to at least one bond pad 304.

In the illustrated embodiment, the stacked dies 308 are coupled to thesubstrate 302 by wire bonds 310, although other connections may be used,such as conductive bumps. In an embodiment, the stacked dies 308 arestacked memory dies. For example, the stacked memory dies 308 mayinclude low-power (LP) double data rate (DDR) memory modules, such asLPDDR1, LPDDR2, LPDDR3, LPDDR4, or the like memory modules. As notedabove, in such embodiments, the bond pads 304 may have a nickel finish304B.

In some embodiments, the stacked dies 308 and the wire bonds 310 may beencapsulated by a molding material 312. The molding material 312 may bemolded on the stacked dies 308 and the wire bonds 310, for example,using compression molding. In some embodiments, the molding material 312is a molding compound, a polymer, an epoxy, silicon oxide fillermaterial, the like, or a combination thereof. A curing step may beperformed to cure the molding material 312, wherein the curing may be athermal curing, a UV curing, the like, or a combination thereof.

In some embodiments, the stacked dies 308 and the wire bonds 310 areburied in the molding material 312, and after the curing of the moldingmaterial 312, a planarization step, such as a grinding, is performed toremove excess portions of the molding material 312 and provide asubstantially planar surface for the device package 300.

After the device package 300 is formed, the device package 300 ismechanically and electrically bonded to the device package 200 by way ofconductive connectors 314, the bond pads 304, and the metallizationpattern 108. In some embodiments, the stacked memory dies 308 arecoupled to the integrated circuit dies 124 through the wire bonds 310,bond pads 303 and 304, through vias 306, conductive connectors 314,through vias 122, and front-side redistribution structure 142.

The conductive connectors 314 may be similar to the conductiveconnectors 146 described above and the description is not repeatedherein, although the conductive connectors 314 and the conductiveconnectors 146 need not be the same. The conductive connectors 314 maybe disposed on an opposing side of the substrate 302 as the stackedmemory dies 308. In some embodiments, a solder resist (not shown) mayalso be formed on the side of the substrate 302 opposing the stackedmemory dies 308. The conductive connectors 314 may be disposed inopenings in the solder resist (not shown) to be electrically andmechanically coupled to conductive features (e.g., the bond pads 304) inthe substrate 302. The solder resist may be used to protect areas of thesubstrate 302 from external damage.

In some embodiments, before bonding the conductive connectors 314, theconductive connectors 314 are coated with a flux (not shown), such as ano-clean flux. The conductive connectors 314 may be dipped in the fluxor the flux may be jetted onto the conductive connectors 314. In anotherembodiment, the flux may be applied to the surfaces of the metallizationpatterns 108.

In some embodiments, the conductive connectors 314 may have an optionalepoxy flux (not shown) formed thereon before they are reflowed with atleast some of the epoxy portion of the epoxy flux remaining after thedevice package 300 is attached to the device package 200. This remainingepoxy portion may act as an underfill to reduce stress and protect thejoints resulting from the reflowing the conductive connectors 314.

Optionally, an underfill material 316 may be formed between the devicepackages 200 and 300. In an embodiment, the underfill material 316 is aprotective material used to cushion and support the device packages 200and 300 from operational and environmental degradation, such as stressescaused by the generation of heat during operation. The underfillmaterial 316 may be injected or otherwise formed in the space betweenthe device packages 200 and 300 and may, for example, be a liquid epoxythat is dispensed between the device packages 200 and 300, and thencured to harden.

FIGS. 16A, 16B, 16C, and 16D are detailed views of the conductiveconnectors 314 and metallization patterns 108 after a bonding process isperformed to physically and electrically couple the device packages 200and 300. The bonding between the device packages 200 and 300 may besolder bonding. In an embodiment, the device package 300 is bonded tothe device package 200 by a reflow process. FIGS. 16A and 16B are,respectively, cross-sectional and plan views showing a connection forthe first redistribution lines 108A. FIGS. 16C and 16D are,respectively, cross-sectional and plan views showing a connection forthe second redistribution lines 108B.

In FIGS. 16A, 16B, 16C, and 16D, the bonding process is performed toreflow the conductive connectors 314 such that they are in contact withthe bond pads 304 and metallization patterns 108. After the bondingprocess, an intermetallic compound (IMC) 318 may form at interfaces ofthe metallization patterns 108 and conductive connectors 314. Becauseexposed portions of the seed layers 106 and 118 were partially or fullyremoved, the IMC 318 may extend partially or completely through themetallization patterns 108. The IMC 318 may also extend laterally alongthe metallization patterns 108 a distance D_(I) from sides of the firstopenings 150.

The bonds formed by the bonding process include the conductiveconnectors 314 (e.g., solder) contacting two different metals. In anembodiment, the metallization patterns 108 are formed of copper, and thebond pads 304 have a nickel finish 304B, resulting innickel-solder-copper connections. When such connections are formed,copper diffuses from the metallization patterns 108 into the conductiveconnectors 314 and toward the nickel finish 304B during reflow. Agradient of diffused copper is formed in the conductive connectors 314,in the direction of the solid arrows. Excessive diffusion of copper fromthe metallization patterns 108 proximate the seed layers 118 may causedelamination of the seed layer 118 from the metallization patterns 108.In particular, diffusion of copper from portions of the metallizationpatterns 108 between the seed layers 118 and the dielectric layer 104may cause delamination of the seed layers 118.

In FIGS. 16A and 16B, the first openings 150A in the dielectric layer104 are disposed laterally a distance D_(O) from portions of the firstvias 122A in the dielectric layer 112. As such, the conductiveconnectors 314 are disposed laterally the distance D_(O) from sides ofthe first vias 122A in a plan view, and are not disposed along thelongitudinal axes of the first vias 122A. The distance D_(O) is chosento be sufficiently large such that the IMC 318A does not extendlaterally to sides of the first vias 122A. In other words, the distanceD_(O) is greater than the distance D_(I), and may be at least twice aslarge as the distance D_(I). In an embodiment, the distance D_(I) may befrom about 2 μm to about 13 μm, such as about 13 μm, and the distanceD_(O) may be from about 25 μm to about 35 μm, such as about 35 μm.Forming the first openings 150A (see, e.g., FIG. 13 ) such that the IMC318A does not extend laterally to sides of the first vias 122A may avoiddiffusion of copper from portions of the first redistribution lines 108Abetween the seed layers 118 and the dielectric layer 104, avoidingdelamination of the seed layers 118.

In FIGS. 16C and 16D, the second openings 150B in the dielectric layer104 are disposed laterally aligned with the gaps 110 in the secondredistribution lines 108B. As such, the conductive connectors 314 arenot spaced laterally from sides of the second vias 122B in a plan view,and are disposed along the longitudinal axes of the second vias 122B.Because exposed portions of the seed layers 106 and 118 were partiallyor fully removed, the IMC 318B extends in a longitudinal direction intothe second vias 122B. Forming the IMC 318B such that it extends into thesecond vias 122B may result in some diffused copper being sourced fromthe second vias 122B, instead of the metallization patterns 108. Thismay reduce the copper diffused from the metallization patterns 108,avoiding delamination of the seed layers 118, and also avoidingreduction of the thickness of the second redistribution lines 108B.

As further shown, the metallization pattern 108 includes slots 322disposed around the periphery of the conductive connectors 314 and thethrough vias 122. The slots 322 provide stress relief, improvingreliability of the electrical connections. In particular, the slots 322provide additional sidewalls for the metallization patterns 108,improving the adhesion between the metallization patterns 108 andpolyimide materials such as the dielectric layer 112. The slots 322 aredisposed at least partially around the conductive connectors 314 in thefirst redistribution lines 108A, and may be disposed completely aroundthe conductive connectors 314 in the second redistribution lines 108B.

In FIG. 17 , a singulation process 320 is performed by singulating alongscribe line regions e.g., between adjacent package regions. In someembodiments, the singulation process 320 includes a sawing process, alaser process, or a combination thereof. The singulation process 320singulates the package region 600 from adjacent package regions (notshown). The resulting package structure 400 is shown after singulation,which may be from the package region 600.

FIG. 18 shows the package structure 400 after it is attached to asubstrate 500. The substrate 500 may be referred to a package substrate500. The package structure 400 is attached to the substrate 500 bymounting the device package 200 to the substrate 500 using theconductive connectors 146.

The package substrate 500 may be made of a semiconductor material suchas silicon, germanium, diamond, or the like. Alternatively, compoundmaterials such as silicon germanium, silicon carbide, gallium arsenic,indium arsenide, indium phosphide, silicon germanium carbide, galliumarsenic phosphide, gallium indium phosphide, combinations of these, andthe like, may also be used. Additionally, the package substrate 500 maybe a SOI substrate. Generally, an SOI substrate includes a layer of asemiconductor material such as epitaxial silicon, germanium, silicongermanium, SOI, SGOI, or combinations thereof. The package substrate 500is, in one alternative embodiment, based on an insulating core such as afiberglass reinforced resin core. One example core material isfiberglass resin such as FR4. Alternatives for the core material includebismaleimide-triazine BT resin, or alternatively, other PCB materials orfilms. Build up films such as ABF or other laminates may be used forpackage substrate 500.

The package substrate 500 may include active and passive devices (notshown. As one of ordinary skill in the art will recognize, a widevariety of devices such as transistors, capacitors, resistors,combinations of these, and the like may be used to generate thestructural and functional requirements of the design for the packagestructure 400. The devices may be formed using any suitable methods.

The package substrate 500 may also include metallization layers and vias(not shown) and bond pads 502 over the metallization layers and vias.The metallization layers may be formed over the active and passivedevices and are designed to connect the various devices to formfunctional circuitry. The metallization layers may be formed ofalternating layers of dielectric (e.g., low-k dielectric material) andconductive material (e.g., copper) with vias interconnecting the layersof conductive material and may be formed through any suitable process(such as deposition, damascene, dual damascene, or the like). In someembodiments, the package substrate 500 is substantially free of activeand passive devices.

In some embodiments, the conductive connectors 146 are reflowed toattach the device package 200 to the bond pads 502. The conductiveconnectors 146 electrically and/or physically couple the packagesubstrate 500, including metallization layers in the package substrate500, to the device package 200. In some embodiments, passive devices(e.g., surface mount devices (SMDs), not illustrated) may be attached tothe device package 200 (e.g., bonded to the bond pads 502) prior tomounting on the package substrate 500. In such embodiments, the passivedevices may be bonded to a same surface of the device package 200 as theconductive connectors 146.

The conductive connectors 146 may have an epoxy flux (not shown) formedthereon before they are reflowed with at least some of the epoxy portionof the epoxy flux remaining after the device package 200 is attached tothe package substrate 500. This remaining epoxy portion may act as anunderfill to reduce stress and protect the joints resulting from thereflowing the conductive connectors 146. In some embodiments, anunderfill (not shown) may be formed between the device package 200 andthe package substrate 500 and surrounding the conductive connectors 146.The underfill may be formed by a capillary flow process after the devicepackage 200 is attached or may be formed by a suitable deposition methodbefore the device package 200 is attached.

Embodiments may achieve advantages. Disposing the conductive connectors314 laterally a sufficient distance D_(O) from sides of the first vias122A in a plan view may avoid diffusion of copper from the metallizationpatterns 108 proximate the seed layers 118. Forming the IMC 318B suchthat it extends into the second vias 122B may result in some diffusedcopper being sourced from the second vias 122B, instead of themetallization patterns 108. Reducing the amount of copper diffused fromthe metallization patterns 108 under the seed layers 118 may avoiddelamination of the seed layers 118, improving the reliability ofresulting devices.

In accordance with some embodiments, a device includes: a first devicepackage including: a first redistribution structure including a firstredistribution line and a second redistribution line; a die on the firstredistribution structure; a first via coupled to a first side of thefirst redistribution line; a second via coupled to a first side of thesecond redistribution line and extending through the secondredistribution line; an encapsulant surrounding the die, the first via,and the second via; and a second redistribution structure over theencapsulant, the second redistribution structure electrically connectedto the die, the first via, and the second via; a first conductiveconnector coupled to a second side of the first redistribution line, thefirst conductive connector disposed along a different axis than alongitudinal axis of the first via; and a second conductive connectorcoupled to a second side of the second redistribution line, the secondconductive connector disposed along a longitudinal axis of the secondvia.

In some embodiments, the device further includes: a second devicepackage including a first bond pad and a second bond pad, the firstconductive connector coupled to the first bond pad, the secondconductive connector coupled to the second bond pad. In someembodiments, the first bond pad and the second bond pad have a nickelfinish. In some embodiments, the first redistribution line and thesecond redistribution line are formed from copper. In some embodiments,the first redistribution structure further includes: a first dielectriclayer, the first redistribution line and the second redistribution linedisposed on the first dielectric layer; and a second dielectric layer onthe first dielectric layer. In some embodiments, the second via islonger than the first via.

In accordance with some embodiments, a method includes: forming a firstredistribution structure including: depositing a first dielectric layerover a carrier substrate; forming a first conductive feature on thefirst dielectric layer; forming a second conductive feature on the firstdielectric layer; forming a third conductive feature on the firstdielectric layer; and depositing a second dielectric layer on the firstconductive feature, the second conductive feature, and the thirdconductive feature; forming a first via on the first conductive feature;forming a second via on the second conductive feature, on the thirdconductive feature, and between the second conductive feature and thethird conductive feature; attaching a die to the first redistributionstructure adjacent the first via and the second via; encapsulating thedie, the first via, and the second via with an encapsulant; planarizingthe encapsulant, the first via, and the second via; and forming a secondredistribution structure over the encapsulant, the first via, the secondvia, and the die.

In some embodiments, the method further includes: debonding the carriersubstrate from the first redistribution structure; and attaching adevice package to the first redistribution structure, the device packageattached to the first conductive feature with a first connector, thedevice package attached to the second conductive feature and the thirdconductive feature with a second connector. In some embodiments, thefirst connector is not disposed along a longitudinal axis of the firstvia. In some embodiments, the second connector is disposed along alongitudinal axis of the second via. In some embodiments, the first viais longer than the second via after the planarizing.

In accordance with some embodiments, a method includes: depositing afirst seed layer on a first dielectric layer; plating a first conductivefeature and a second conductive feature on the first seed layer;depositing a second dielectric layer on the first conductive feature andthe second conductive feature; forming a first opening in the seconddielectric layer, the first opening exposing the first conductivefeature, the second conductive feature, and the first dielectric layer;depositing a second seed layer on the second dielectric layer and in thefirst opening; plating a first via from portions of the second seedlayer in the first opening; attaching a die to the second dielectriclayer; and encapsulating the first via and the die with an encapsulant.

In some embodiments, the method further includes: forming a secondopening in the first dielectric layer, the second opening exposing thefirst seed layer and the second seed layer; forming a reflowablematerial in the second opening, the reflowable material disposed along alongitudinal axis of the first via; and reflowing the reflowablematerial to form an intermetallic compound from the reflowable materialand conductive material of the first seed layer, the second seed layer,and the first via. In some embodiments, the method further includes:attaching a device package to the first conductive feature and thesecond conductive feature with the reflowable material. In someembodiments, reflowing the reflowable material includes diffusingportions of the conductive material of the first via into the reflowablematerial. In some embodiments, the method further includes: forming athird conductive feature on the first dielectric layer; depositing thesecond dielectric layer on the third conductive feature; forming asecond opening in the second dielectric layer, the second openingexposing the third conductive feature; depositing the second seed layerin the second opening; and plating a second via from portions of thesecond seed layer in the second opening. In some embodiments, the methodfurther includes: forming a third opening in the first dielectric layer,the third opening exposing the first seed layer; forming a reflowablematerial in the third opening, the reflowable material disposed along adifferent axis than a longitudinal axis of the second via; and reflowingthe reflowable material to form an intermetallic compound from thereflowable material and conductive material of the first seed layer. Insome embodiments, reflowing the reflowable material includes diffusingportions of the conductive material of the third conductive feature intothe reflowable material. In some embodiments, no portion of theintermetallic compound is formed between the second via and the firstdielectric layer. In some embodiments, the method further includes:planarizing the first via, the second via, and the encapsulant, thefirst via being longer than the second via after the planarizing.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a firstredistribution structure comprising: depositing a first dielectric layerover a carrier substrate; forming a first conductive feature and asecond conductive feature on the first dielectric layer, wherein thesecond conductive feature is provided with a gap that exposes the firstdielectric layer; and depositing a second dielectric layer on the firstconductive feature and the second conductive feature; forming a firstopening and a second opening in the second dielectric layer, wherein thefirst opening exposes the first conductive feature and the secondopening exposes the second conductive feature and the gap; forming afirst via on the first conductive feature and partially in the firstopening; forming a second via on the second conductive feature andpartially in the second opening and the gap; attaching a die to thefirst redistribution structure adjacent the first via and the secondvia; and encapsulating the die, the first via, and the second via withan encapsulant.
 2. The method of claim 1, further comprising:planarizing the encapsulant, the first via, and the second via.
 3. Themethod of claim 1, further comprising: forming a second redistributionstructure over the encapsulant, the first via, and the second via. 4.The method of claim 3, further comprising: forming conductive connectorsover the second redistribution structure such that the die and theconductive connectors are on opposite sides of the second redistributionstructure.
 5. The method of claim 1, wherein the first and the secondconductive features are formed over a first side of the first dielectriclayer, further comprising: removing the carrier substrate to expose asecond side of the first dielectric layer that is opposite to the firstside of the first dielectric layer; and forming a third opening into thefirst dielectric layer from the second side of the first dielectriclayer, wherein the third opening overlaps with the gap in the secondconductive feature along a thickness direction of the first dielectriclayer.
 6. The method of claim 5, further comprising: forming a fourthopening into the first dielectric layer from the second side of thefirst dielectric layer, wherein a centerline of the fourth opening isoffset from a centerline of the first via.
 7. The method of claim 6,wherein the fourth opening and the first opening do not overlap alongthe thickness direction of the first dielectric layer.
 8. A devicecomprising: a first redistribution structure comprising a firstconductive line and a second conductive line; an integrated circuit dieattached to the first redistribution structure; a first via coupled tothe first conductive line; a second via coupled to the second conductiveline, wherein the second via has a height greater than a height of thefirst via, the first via has one or more changes in width, the secondvia has one or more changes in width, and the second via has morechanges in width than the first via has; an encapsulant surrounding theintegrated circuit die, the first via, and the second via; and a secondredistribution structure over the encapsulant, the second redistributionstructure being electrically connected to the first via, the second via,and the integrated circuit die, wherein the first and the secondredistribution structures are on opposite sides of the integratedcircuit die.
 9. The device of claim 8, further comprising: firstconductive connectors over the second redistribution structure such thatthe integrated circuit die and the first conductive connectors are onopposite sides of the second redistribution structure.
 10. The device ofclaim 9, further comprising: second conductive connectors over the firstredistribution structure such that the integrated circuit die and thesecond conductive connectors are on opposite sides of the firstredistribution structure.
 11. The device of claim 10, furthercomprising: a device package with one or more dies, wherein the devicepackage is electrically bonded to the second conductive connectors. 12.The device of claim 10, wherein one of the second conductive connectorsis disposed on the second conductive line and overlaps with the secondvia along a thickness direction of the first redistribution structure.13. The device of claim 10, wherein one of the second conductiveconnectors is disposed on the first conductive line, and a centerline ofthe one of the second conductive connectors is offset from a centerlineof the first via.
 14. The device of claim 8, wherein the first via hasone change in width and the second via has two changes in width.
 15. Adevice comprising: a first redistribution structure comprising a firstconductive line and a second conductive line disposed in a firstdielectric layer; a die attached to the first redistribution structure;a first via coupled to the first conductive line; a second via coupledto the second conductive line and extending through the secondconductive line; a first intermetallic compound contacting the firstconductive line; a second intermetallic compound contacting the secondconductive line and the second via; an encapsulant surrounding the die,the first via, and the second via; a first conductive connector disposedon the first intermetallic compound, wherein the first conductive lineand the first conductive connector are disposed on opposite sides of thefirst intermetallic compound; and a second conductive connector disposedon the second intermetallic compound, wherein the second conductive lineand the second conductive connector are disposed on opposite sides ofthe second intermetallic compound.
 16. The device of claim 15, whereinthe second conductive connector overlaps with the second via along athickness direction of the first redistribution structure.
 17. Thedevice of claim 15, wherein the first conductive connector is offsetfrom the first via along a thickness direction of the firstredistribution structure.
 18. The device of claim 15, wherein the firstintermetallic compound is offset from the first via along a thicknessdirection of the first redistribution structure.
 19. The device of claim15, further comprising: a device package electrically bonded to thefirst and the second conductive connectors, wherein the device packageand the die are on opposite sides of the first redistribution structure.20. The device of claim 19, further comprising: a second redistributionstructure over the encapsulant and electrically connected to the firstand the second vias, wherein the die is sandwiched between the first andthe second redistribution structures.